1. Field of the Invention
The present invention relates to a film winding system of a camera, and specifically relates to a film feeding system at initial loading of the camera.
2. Description of the Related Art
An operation of initial loading in conventional cameras is, generally, so arranged that a releasing operation is preformed every time a frame of the film roll is wound and the initial load operation is completed at the time when three or four frames of the film roll have been wound. This is caused by the following. That is, a cocking operation to a diaphragm, a mirror, and a shutter is effected by an operation of film winding, so that a subsequent film winding operation to the preceding is not effected unless otherwise the releasing operation is carried out. The releasing operation at the initial loading is meaningless originally. On one hand, conventionally, there are provided cameras having a motor driven film winding system, widely. In such cameras, if the same procedure mentioned above is applied, one of merits of the motor driven system is lost. Accordingly, there are, recently, provided motor-drive type cameras which are capable of carrying out the initial loading without the cocking operation. This type of cameras has two driving motors and corresponding transmission devices by which the film winding operation and the cocking operation are effected independently. And at the initial loading, one of the motors is driven and only the film winding apparatus is driven through the transmission device corresponding to the motor. However, there are the following disadvantages in this type of the cameras. This is, the two driving systems are required, so that a spacing problem and a cost problem of a camera are arisen.
In connection with the initial loading of a camera, there are provided cameras further having a function of automatic film feeding operation at the initial loading, in recent. This function is to automatically feed the film roll to a spool and to wind the film roll therearound automatically at the initial loading, and this function is realized by the above-mentioned mechanism. From a point of view on its mechanism, a confirmation of film winding around the spool is important. In this field, one of conventional technique is as follows. A switch is arranged between a film pressing roller and a spool, and the switch is turned off when the film roll is inserted therebetween. Then, the initial loading is successful. There is a disadvantage in this case that a wrong decision may be made. That is, a positive decision is made under the condition that the film roll is just positioned between the two nevertheless the film roll is not wound around the spool.
Another conventional technique is available. In a camera having a spool, driven by a motor, for winding the film roll and a film sprocket, driven by the motor or any other motor, for feeding the film roll to the spool, a mechanism is so arranged that the film sprocket gets rid of the motor drive and becomes completely free at a last half of the initial loading process, and pulse signals are generated by rotating of the sprocket, and it is decided on the basis of the pulse signal whether or not a film feeding operation is successful. A disadvantages of this mechanism is to become complicated and costly.
As previously described, the releasing operation at the initial loading is meaningless from a photographing point of view. However, a photographer makes often the releasing operation under the condition of no film roll loaded in a camera for trial shooting and/or a confirmation whether or not the camera functions well before photographing. Therefore, it is preferable that the releasing operation of the camera becomes possible even in the case of where no film roll is loaded in the camera.
In order to accomplish the above-mentioned operation, various types of mechanisms are provided. One of those, for example, two operation modes are provided for a camera. One is for normal photographing, and the other is for a trial purpose of the camera function. Depending on the photographer's intention, he switches over to one of the modes, then a driving mechanism is controlled electrically in accordance with the selected mode. This type causes decrease of operability of the camera, as well as, extra parts and/or devices are requested, resulting in that it causes a cost problem. On one hand, as previously described, in the two motors driving-type camera, the abovementioned operation is quite easily enabled with electrical controlling of the driving mechanism. However, the cost problem and the spacing problem are left as it are.